In looking at a range of various film openings, there are various elements which are applied.
Firstly, the camera shots/angles which are used play a big part in setting the tone of the film. I have noticed that in horror films the camera angles are either high angles, panning shots or point of view shots. For instance in Halloween, a point of view shot is used which is focused on a sub-urban house. To give a dramatic effect the camera is not still but it is shaking in order to build up tension and suspense but also to show the vulnerability of the victims inside the house. Shots like these are used to create narrative enigma for the audience as they do not see the killers face straight away. Also, another example of a point of view shot is in Jennifer's Body. Like Halloween, there is a point of view shot of the supposed "killer" which shows the house in the opening scene. Due to this trend, point of view shots are used to set the scene and to provide details on the background, social status and the overall feel of the neighborhood.
Secondly, sound also contributes to the film openings as it not only provides anchorage for the genre, but it sets the mood for the first opening minutes. For instance, in 5ive Girls, there is a diagetic sound of an organ which sets the tone of film as it provides a haunting and oppressive tone. However, sound can also portray the time period as we see in Hell Night. Diagetic sound is being played from a radio and it is typical rock music sung by a woman, and this therefore signifies the time period. In the opening sequence for Halloween, the non-diagetic music is fast paced with a combination of slow string notes which brings an eeriness.
Thirdly, I have seen throughout various slasher films that they each have a tint to the lens. This blue tint is used to signify that it is night time in most of the films. Most of these have blue tints such as Bride of Chucky, Peeping Tom and Halloween. However, some use red or orange tints to signify danger such as A Nightmare On Elm Street.